Modeling of Marine Immersion Corrosion for Mild and Low-Alloy Steels—Part 1: Phenomenological Model

A model is proposed for general corrosion of mild and low-alloy steels under fully aerated at-sea immersion conditions as measured by weight loss. Because all factors influencing corrosion have inherent uncertainties, the proposed model is probabilistic, composed of a mean-value function and a zero-mean uncertainty function. The mean-value function is nonlinear in time, controlled by distinctly different phases—kinetic, diffusion, and anaerobic. Literature field data as well as new field observations indicate that seawater temperature has a strong influence on each phase. The model is used to interpret literature data together with additional inferred or collected environmental data. These are then used to calibrate the parameters for the mean-value function of the model. The calibrated parameters are used to predict a consolidated plot of expected corrosion loss—time-temperature. An example application is given.